Dynamo electric machines, and especially alternators of the automotive type, in operation, cause noise which may be due to chatter or hum of laminations which vibrate with respect to each other. In automotive apparatus, which operates at highly variable speeds, the pitch of the generated noise changes with speed of the engine driving the alternator. It is particularly annoying at various speeds, where resonance effects may occur.
Alternators, especially of the vehicular type, usually have two end shields or end disks or end bells between which a stator package is clamped. The stator package customarily is formed of a plurality of essentially ring-like stator laminations, stacked together to form the stator magnetic circuit. The end bells form supports for accessory equipment, as well as for the bearings for a rotor, rotating within the stator.